Ehlers Fourier Series Indicator (FSI)

Category: cycle

The FSI (Fourier Series Indicator) by John Ehlers uses bandpass filters and their quadrature components to reconstruct the price action as a sum of the first three harmonics of a fundamental cycle.

Formula

\begin{aligned} 
BP_n &= 0.5(1-S_n)(Price - Price[2]) + L_n(1+S_n)BP_n[1] - S_n BP_n[2] \\
Q_n &= \frac{T_n}{2\pi}(BP_n - BP_n[1]) \\
P_n &= \sum_{i=0}^{x} (BP_{n,i}^2 + Q_{n,i}^2) \\
FSI &= BP_1 + \sqrt{\frac{P_2}{P_1}}BP_2 + \sqrt{\frac{P_3}{P_1}}BP_3
\end{aligned}

Inputs

• Fundamental Cycle Period (default: 20)
• Bandwidth (default: 0.1)

See signal primitives, usage in published strategies and more on WOBR StrategyVerse.